A door harp is a flat, hollow box with hanging balls gently bouncing off strings that are tuned to different notes. These often ornate ornaments can include just three or as many as a dozen or more strings, for either a simple or complex panoply of sound that changes with the breeze when placed outside the home. When placed on the inside, as is traditional, a door harp will produce a distinctive noise for the inhabitants whenever the door is opened and closed.
The door harp originated in Scandinavia — primarily in Sweden, but also in Norway and Denmark — and has evolved over at least three centuries. Some estimate these ornaments have been made for as long as 700 years, derived from a few styles of Chinese stringed instruments called the guqin and the ruan. The door harp is not meant to be played, however, just enjoyed.
Made of various hardwoods, door harps are fashioned into thin soundboard boxes, with one or more sound holes in front. The shapes of the boxes range from hearts, tears or ovals to round, square or rectangular. The more unusual the design, the more prized it will be be as a work of art. These hangings are typically finished with lacquer, lemon oil or beeswax. Designs also can be found painted onto their fronts.
The number of strings on a door harp determines the complexity of the sound it will make. Wooden clapper balls are hung from vertical strings of varying length that are attached in a single row along the top of the door harp. Each vertical string will allow its ball to descend to a different horizontal string. There is one ball per horizontal string, from a minimum of three to a dozen or more notes, so that when the balls bounce they produce warbling chords of random music.
Some use a tuning wrench to tighten the end points, or zither pins, on their door harp. This way it will produce a perfectly tuned set of notes. The strings are usually made of wire, but some are made the traditional way with braided silk.
Some people hang their door harps on the outside of a door to greet visitors or on the wall somewhere near an open window. It is traditional, however, to hang them inside the front door so that music will sound anytime someone comes or goes. As well as homes, many shops in Sweden will have a door harp inside to alert the shopkeeper of a new customer's presence.